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Grades K–2 · Machines

How does a door swing on a hinge?

A door swings open because small joints called hinges hold one edge to the frame while letting the door turn. Inside an ordinary hinge, metal pieces turn around a pin. The pin stays in the same place.

When someone pushes the door, the edge near the hinge stays close to the frame. The handle on the far edge travels along a much bigger curve. All parts of the door turn together, but they do not travel the same distance.

The small hinge circle stays at the corner in both views. The handle moves around it.

One door, two positionsTwo overhead views show the same hinge at the frame. The door changes from shut to open, with its handle following a curved path around the fixed hinge.One fixed hingeShutOpenHandlemovesHinge stays beside the frame.
The same door is shown shut and open from above. The hinge stays in place while the handle follows a curve.

The picture looks down from above. It shows the same door shut and open. The curved line marks the handle’s journey.

That swing needs empty space beside the doorway. A hinge keeps the door attached while making a clear opening for someone to walk through.

About this explanation

Starting knowledge: Recognize a door; point to left, right, open and shut with adult support.

Sources

  • OpenStax — 12.2 Examples of Static Equilibrium: Forces on Door Hinges
  • NGSS / National Science Teaching Association — K-2-ETS1-2 Engineering Design
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